Communication Disorders: An Introduction for Community-Based Rehabilitation Workers

6. Speech Problems

6 Speech Problems Introduction Speech is the primary means by which most people convey their language - or mutually understood code - to others. In terms of assessment and remediation, it is important to understand the difference between speech and language. By speech we mean the articulatory process through which sounds and words are produced in the vocal tract. Speech and language are mutually dependent and therefore care must be exercised in considering them as separate entities. Speech includes both the perception and production of sound. Speech perception is a complex function heavily dependent on the hearing and processing of sound sequences according to the rules of a given language. Sound can be discriminated, described or reproduced according to its acoustic properties. Those people who have difficulty with speech discrimination and processing will usually have trouble with speech production. Speech production is a motor act involving the use of the lungs, larynx (vocal cords/folds) and organs of articulation in the mouth. Speech production includes respiration, phonation, resonance, articulation and prosody; each ofwhich will be discussed individually. Speech perception is dependent on the auditory cortex of the brain but the two primary centres for speech production are in the left hemisphere of the brain in most individuals. People of all ages can suffer from speech disorders. These may result from many different aetiologies of either central or peripheral origin. They can be caused by neuromuscular or orofacial disorders and pathologies as well as by hearing loss or emotional and developmental problems and delay. Even a comparatively mild speech disorder such as a lisp can have a 44 Communication Disorders profound effect upon an individual's life and ability to communicate. Many speech disorders can be overcome with appropriate remediation. Medical background The anatomy and neurophysiology of the peripheral and central hearing mechanisms associated with the perception of speech are briefly described in Chapter 8, Hearing Disability. Anatomy of the peripheral speech mechanism hard palate soft palate (velum) lips +--~- pharynx /+----+-- epiglottis ~.r----Iarynx Figure 6.1 The principal organs of speech production. Speech production depends on air being forced up from the lungs by way of the trachea and into the vocal tract which contains: • the larynx • pharynx • tongue • soft palate • hard palate • teeth • lips Speech Problems 45 Speech production 1. The respiratory system builds up the air flow. 2. The sound produced by the vibrations of the vocal cords is eventually forced out through the mouth and influenced by the position of the various speech organs in the mouth. 3. The amount of air pressure below the glottis (the opening between the vocal cords) will contribute to the loudness of the voice. 4. The length and vibration of the cords will affect the resulting pitch of the voice. 5. The pharynx acts as a resonator for the sound. 6. The rapidly changing positions of the lips, teeth, tongue and soft palate will influence the air flow and produce the vowels and consonants that we recognize as speech. The central speech system 1. Sensory information from the orofacial region and vocal tract is provided by branches of the trigeminal (5th), facial (7th), glossopharyngeal (9th), vagus (10th) and hypoglossal (12th) cranial nerves. 2. The thalamus is the major relay centre for the sensory information to be transferred to the speech areas of the cortex. 3. The two primary areas of the cortex to be involved in speech (and language) are Broca's Area and Wernicke's Area, both of which are located in the left hemisphere of the brain. 4. The sensorimotor cortex exercises control over voluntary movement of the speech mechanism. 5. Both the pyramidal and extrapyramidal systems are important to speech; abnormalities in these systems may cause speech disorders. 6. The cerebellum is important for motor control of speech; its dysfunction may produce the speech disorder known as dysarthria, characterized by an inability to articulate clearly. 7. Nuclear groups of the brainstem provide the final common pathway for signals sent from the cortex to the cranial nerves serving the speech mechanisms. Pathologies resulting in speech disorders and their medical management Speech disorders can be caused by: • hearing loss • pathologies of the central auditory system • pathologies of the central speech system • problems with the peripheral mechanism 46 Communication Disorders • orofacial anomalies • developmental problems • emotional problems Specific medical management for many of the resulting disorders is discussed in the relevant chapters on hearing loss, cleft palate, voice disorders, stroke and the non...